请写一串开发板代码，使之有以下功能：1 开发板上选三个LED，分别设置为 红灯、绿灯、黄灯（板子上都是红色，可以标记一下）其中，红灯10秒，绿灯15秒，黄闪5秒，往返循环 2 数码管显示当前信号灯的倒计时 3 USB转串口，接串口调试助手，可以实时输出：当前灯色+剩余时间

好的，以下是一个基于STM32的开发板代码，实现了你所要求的功能：

#include "stm32f10x.h"
#include <stdio.h>

// 定义LED端口和引脚
#define RED_LED_PIN     GPIO_Pin_0
#define GREEN_LED_PIN   GPIO_Pin_1
#define YELLOW_LED_PIN  GPIO_Pin_2
#define LED_PORT        GPIOC

// 定义数码管引脚
#define DIGIT1_PIN      GPIO_Pin_0
#define DIGIT2_PIN      GPIO_Pin_1
#define DIGIT3_PIN      GPIO_Pin_2
#define DIGIT4_PIN      GPIO_Pin_3
#define DIGIT_PORT      GPIOB

// 定义红绿黄灯的时间
#define RED_TIME        10
#define GREEN_TIME      15
#define YELLOW_TIME     5

// 定义状态枚举类型，表示当前灯的状态
typedef enum {
    RED,
    GREEN,
    YELLOW
} LightState;

// 定义全局变量，表示当前灯的状态和剩余时间
LightState lightState = RED;
int remainingTime = RED_TIME;

// 定义函数，用于控制灯的状态
void setLightState(LightState state) {
    switch (state) {
        case RED:
            GPIO_SetBits(LED_PORT, RED_LED_PIN);
            GPIO_ResetBits(LED_PORT, GREEN_LED_PIN);
            GPIO_ResetBits(LED_PORT, YELLOW_LED_PIN);
            break;
        case GREEN:
            GPIO_ResetBits(LED_PORT, RED_LED_PIN);
            GPIO_SetBits(LED_PORT, GREEN_LED_PIN);
            GPIO_ResetBits(LED_PORT, YELLOW_LED_PIN);
            break;
        case YELLOW:
            GPIO_ResetBits(LED_PORT, RED_LED_PIN);
            GPIO_ResetBits(LED_PORT, GREEN_LED_PIN);
            GPIO_SetBits(LED_PORT, YELLOW_LED_PIN);
            break;
    }
}

// 定义函数，用于控制数码管显示剩余时间
void setDigit(int digit) {
    GPIO_ResetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT2_PIN | DIGIT3_PIN | DIGIT4_PIN);
    switch (digit) {
        case 0:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT2_PIN | DIGIT3_PIN);
            break;
        case 1:
            GPIO_SetBits(DIGIT_PORT, DIGIT2_PIN | DIGIT3_PIN);
            break;
        case 2:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT2_PIN | DIGIT4_PIN);
            break;
        case 3:
            GPIO_SetBits(DIGIT_PORT, DIGIT2_PIN | DIGIT4_PIN);
            break;
        case 4:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT3_PIN | DIGIT4_PIN);
            break;
        case 5:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT4_PIN);
            break;
        case 6:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT2_PIN | DIGIT3_PIN | DIGIT4_PIN);
            break;
        case 7:
            GPIO_SetBits(DIGIT_PORT, DIGIT2_PIN | DIGIT3_PIN | DIGIT4_PIN);
            break;
        case 8:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT2_PIN | DIGIT3_PIN | DIGIT4_PIN);
            break;
        case 9:
            GPIO_SetBits(DIGIT_PORT, DIGIT1_PIN | DIGIT3_PIN | DIGIT4_PIN);
            break;
    }
}

// 定义函数，用于初始化GPIO口
void initGPIO() {
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOC, ENABLE);

    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

    GPIO_InitStructure.GPIO_Pin = RED_LED_PIN | GREEN_LED_PIN | YELLOW_LED_PIN;
    GPIO_Init(LED_PORT, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = DIGIT1_PIN | DIGIT2_PIN | DIGIT3_PIN | DIGIT4_PIN;
    GPIO_Init(DIGIT_PORT, &GPIO_InitStructure);

    GPIO_SetBits(LED_PORT, RED_LED_PIN);
    GPIO_ResetBits(LED_PORT, GREEN_LED_PIN);
    GPIO_ResetBits(LED_PORT, YELLOW_LED_PIN);
}

int main(void) {
    initGPIO();

    // 初始化串口
    USART_InitTypeDef USART_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
    USART_InitStructure.USART_BaudRate = 115200;
    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
    USART_InitStructure.USART_StopBits = USART_StopBits_1;
    USART_InitStructure.USART_Parity = USART_Parity_No;
    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStructure.USART_Mode = USART_Mode_Tx;
    USART_Init(USART1, &USART_InitStructure);
    USART_Cmd(USART1, ENABLE);

    while (1) {
        // 更新剩余时间
        remainingTime--;

        // 判断是否需要切换灯的状态
        if (remainingTime == 0) {
            switch (lightState) {
                case RED:
                    lightState = GREEN;
                    remainingTime = GREEN_TIME;
                    break;
                case GREEN:
                    lightState = YELLOW;
                    remainingTime = YELLOW_TIME;
                    break;
                case YELLOW:
                    lightState = RED;
                    remainingTime = RED_TIME;
                    break;
            }
            setLightState(lightState);
        }

        // 计算数码管显示的数字
        int digit = remainingTime % 10;

        // 控制数码管显示数字和灯的状态
        setDigit(digit);
        char message[256];
        sprintf(message, "%s %d\n", lightState == RED ? "RED" : lightState == GREEN ? "GREEN" : "YELLOW", remainingTime);
        USART_SendData(USART1, message);
        for (int i = 0; i < 1000000; i++);  // 延时一段时间
    }
}

需要注意的是，这段代码只是一个简单的示例，实际开发中可能需要根据硬件平台和具体需求进行修改。